基于制造成本与质量损失的并行公差设计

研究产品质量损失与产品尺寸公差的关系 ,提出具有多个相关装配尺寸产品的质量损失 ,并把它表示成工序公差的函数。利用成本 -公差函数和产品的质量损失函数 ,给出基于产品最低制造成本和多个相关装配尺寸产品质量损失的并行公差设计优化模型 ,实现公差的并行设计 ,最后通过工程实例验证所提出的方法     

基于信噪比多元质量损失和制造成本的并行公差设计

质量损失是由于产品的功能波动所造成的,损失大小可由质量函数确定。在无量纲“标准化”多元质量损失函数的基础上,采用信噪比衡量各质量指标的波动,建立一般情形下的基于信噪比的多元质量损失模型,并把它表示成多个相关装配尺寸产品的工序公差函数。利用成本-公差函数和产品质量损失函数,给出基于产品最低制造成本和多个相关装配尺寸产品质量损失的并行公差设计优化模型,实现公差的并行设计,最后通过工程实例验证所提出的方法。     

多工序尺寸及公差优化

为提高产品制造质量、降低产品制造成本,提出了一种多工序尺寸及公差的优化方法.该方法综合考制造成本、质量损失和加工能力指数,以加工能力指数分别修正制造成本一公差函数和质量损失函数,在工序内建立总成本一公差函数模型.在此基础上,采用目标层解法优化特征内的各个工序基本尺寸和尺寸公差,最终达降低特征总成本的目的.最后以一个仿真实例验证了该方法的可行性.     

基于多重相关特征质量损失函数的公差优化设计

在重点推导了具有多重相关特征产品的质量损失与尺寸公差的函数关系的基础上,提出了多重相关特征产品的公差优化设计方法,建立了基于制造成本一质量损失的公差优化设计的综合模型,建立该模型的目的是寻求制造成本和质量损失之间的平衡,实现旨在提高产品质量和降低成本的公差优化设计。应用实例验证了所提出方法的有效性。     

一种设计和工序公差计算机辅助并行设计方法的研究

提出一种计算机辅助设计公差和工序公差并行设计的数学模型，以成本公差函数作为目标函数，以装配功能要求、加工方法、加工余量、工序制造公差范围作为约束条件，并用蒙特卡洛法模拟尺寸装配、模拟退火算法用于优化求解，实现了设计公差和工序公差并行设计，缩短了设计周期。     

基于资金时间价值的并行公差优化设计

总结了经典的成本公差模型,基于资金的时间价值原理对经典成本公差模型进行优化,提出了多种优化后的成本公差模型计算方法。利用优化后的成本公差模型,将制造成本、质量损失成本同时考虑到并行公差设计的目标函数中,实现了并行公差的优化设计。通过工程实例证明了所提方法的有效性,结果表明,优化后的成本公差模型更贴近实际,计算得到的总成本更为合理,有效地反应了物价上涨、通货膨胀、资金的时间价值等现实因素。     

基于最短路径的复杂机械产品装配过程质量控制点公差带在线优化方法

为提高复杂机械产品的装配精度和装配质量稳定性,提出一种基于最短路径的复杂机械产品装配过程质量控制点公差带在线优化方法。对关键工序的质量控制点公差带进行细粒度划分;从装配精度角度出发,引入田口工序能力指数构建质量损失—公差函数;综合考虑装配过程中两种作业(基本作业和辅助作业)类型的时间调整损失,建立装配时间调整费用—公差函数;在上述两函数的基础上,通过加权聚类建立装配损失—公差函数模型,以描述质量控制点的总损失与公差的关系;构建基于最短路径的公差带在线优化模型,将装配损失—公差函数作为权函数,以最小损失为目标进行搜索,实现对后续质量控制点公差带的在线优化。以某型发动机缸盖螺栓拧紧过程为应用实例,验证了上述方法的可行性和有效性。     

基于粒子群算法的公差分配优化方法

基于成本—公差模型和质量损失模型,以加工能力和装配尺寸链的功能约束条件为标准,以制造成本最低、质量损失最小为优化目标,建立兼顾产品成本和质量的公差分配的多目标函数优化模型。基于粒子群优化算法,按照从全局到局部的寻优策略,用线性调节方法来确定其参数的变化规律,进而应用MATLAB软件对建立的函数模型进行优化计算,得到产品的生产成本和质量损失之间的关系曲线,可为公差分配提供更多的解决方案和更可靠的理论依据。     

基于广义装配原理的产品生长型设计

通过研究生物生长与产品设计之间的相似性,提出了基于广义装配原理的生长型设计过程,研究了广义装配原理的三个理论构成。首先,在产品生长阶段,为实现生长过程中的自然选择,提出了以复杂度理论为控制因素的设计推理策略;其次,提出了功能公差设计理论,通过加工成本以及基于多因素的模糊质量损失成本体现广义装配成本,在确保产品功能的同时,以较低的装配与制造成本为公差的分配策略;在产品进化阶段,为保证产品良好的装配性能,采用了虚实结合设计技术。将以装配质量因素为核心的产品复杂度、精度以及制造、装配成本等众多设计因素并行集成于生长型设计过程中,实现了以全生命周期装配质量保障为核心的产品生长型设计。     

基于广义装配原理的产品生长型设计

通过研究生物生长与产品设计之间的相似性,提出了基于广义装配原理的生长型设计过程,研究了广义装配原理的三个理论构成.首先,在产品生长阶段,为实现生长过程中的自然选择,提出了以复杂度理论为控制因素的设计推理策略;其次,提出了功能公差设计理论,通过加工成本以及基于多因素的模糊质量损失成本体现广义装配成本,在确保产品功能的同时,以较低的装配与制造成本为公差的分配策略;在产品进化阶段,为保证产品良好的装配性能,采用了虚实结合设计技术.将以装配质量因素为核心的产品复杂度、精度以及制造、装配成本等众多设计因素并行集成于生长型设计过程中,实现了以全生命周期装配质量保障为核心的产品生长型设计.     

Concurrent process tolerance design based on minimum product manufacturing cost and quality loss

In a concurrent design environment, a robust optimum method is presented to directly determine the process tolerances from multiple correlated critical tolerances in an assembly. With given distributions of multiple critical assembly dimensions, the Taguchi quadric quality loss function is first derived. The quality loss is then expressed as the function of pertinent process tolerances. A nonlinear optimal model is established to minimize the summation of manufacturing costs and product quality loss. An example illustrates the proposed model and the solution method .     

Computer-aided geometrical dimensioning and tolerancing for process-operation planning and quality control

This paper describes an extension of a model which determines an optimum set of dimensions and tolerances for machining processes at minimum manufacturing cost. This optimisation minimizes the cost of scrap, which is a function of manufacturing tolerances, as the objective function. Requirements of design sizes, geometrical tolerances (including both form and position) and machining allowances are expressed mathematically as constraints for the optimisation. A computerised trace method has been extended to determine the relationships between geometrical tolerances and associated relevant manufacturing dimensions and tolerances. In addition to the manufacturing cost, the model takes into account manufacturing sequence, distribution of manufacturing dimensions, process capabilities, tolerances, design sizes, geometrical tolerances, machining allowances and optimum scrap level. The resulting computerized interactive system can be used not only in process planning, but also in quality control.     

Optimal tolerance design of assembly for minimum quality loss and manufacturing cost using metaheuristic algorithms

Tolerance allocation is a design tool for reducing overall cost of manufacturing while meeting target levels for quality. An important consideration in product design is the assignment of design and manufacturing tolerances to individual component dimensions so that the product can be produced economically and functions properly. The allocation of tolerances among the components of a mechanical assembly can significantly affect the resulting manufacturing costs. In this work, the tolerance allocation problem is formulated as a non-linear integer model by considering both the manufacturing cost of each component by alternate processes and the quality loss of assemblies so as to minimise the manufacturing cost. Metaheuristics techniques such as genetic algorithm and particle swarm optimisation are used to solve the model and obtain the global optimal solution for tolerance design. An example for illustrating the optimisation model and the solution procedure is provided. Results are compared with conventional technique and the performances are analysed.     

Process capability-based tolerance design to minimise manufacturing loss

In this paper we propose a nonlinear programming model, composed of a cumulative standard normal probability function and manufacturing cost, to design process tolerances. The tolerances are standardised in conjunction with the process capability of the machinery to minimise the total manufacturing loss that occurs owing to non-conforming parts. The proposed model has been applied to a workpiece manufactured through ten operations and solved by GINO (General INteractive Optimizer). A comparison between the results obtained by the proposed model and other methods indicates that robust process tolerances can be obtained by the new formulation.     

Concurrent tolerancing for design and manufacturing based on the present worth of quality loss

The quality loss function developed by Taguchi provides a monetary measure for the deviation of the product quality characteristic from the target value. Product use causes degradation on its quality characteristic, and since such a deviation can be changing over time, so can the quality loss. However, most studies on concurrent tolerancing theory do not consider the quality loss caused by the degradation. In this paper, the present worth of expected quality loss expressed as the function of the pertinent process tolerances in a concurrent tolerancing environment is derived to capture the quality loss due to product degradation over time as a continuous cash flow function under continuous compounding. A new tolerance optimization model, which is to minimize the summation of manufacturing cost and the present worth of expected quality loss, is established to realize the concurrent tolerance allocation for products with multiple quality characteristics. An example of the bevel gear assembly involving concurrent allocation of design and process tolerances is given, demonstrating that the proposed model is feasible in practice.     

基于宽容分层序列法的飞机装配公差稳健设计技术

飞机制造中由于工序能力指数和公差等设计变量存在变差,可能导致无法满足飞机装配质量要求以及制造成本波动较大的问题。运用稳健设计方法建立了飞机装配公差的可行稳健性和敏感稳健性两类设计模型。可行稳健设计考虑了公差等设计变量对装配可行性的影响,使其变差不影响装配功能的实现;敏感稳健性设计则考虑了公差等设计变量对制造成本和装配质量的影响,在目标成本较小的前提下使得目标成本和装配质量受设计变量变差的影响最小。提出了针对飞机装配公差可行敏感稳健设计的多目标优化问题的宽容分层序列求解算法。将公差设计中制造成本、装配质量波动、制造成本波动多个设计目标按照重要性依次排序。首先求解成本最小情况下的公差一般优化解,然后在成本最小值的宽容约束下,求得具有装配质量波动最小值的公差,最后在上述两个优化目标的宽容约束下,求得成本波动最小的最优公差。应用实例和分析结果表明了方法的有效性。       

Tolerance chart balancing with a complete inspection plan taking account of manufacturing and quality costs

This paper introduces a mathematical model of tolerance chart balancing for machining process planning under complete inspection. The criteria considered in this study are based on the combined effects of manufacturing cost and quality loss, under constraints such as process capability limits, product design specifications, and product quality requirements. Manufacturing costs include the machining cost, part cost, inspection cost, reworking cost, and replacement cost. The machining cost is expressed in geometrical decreasing functions, which represent tolerances to be assigned. Process variability is expressed in quadratic loss functions, which represent the deviation between the part measurement and the target value. An example is presented to demonstrate the proposed model. A comparison made with previous methods shows that the proposed model minimizes the total cost of manufacturing activities and quality-related issues in machining process planning, particularly in the early stages. Moreover, the applications are not be limited to machining process planning but can also be used in other forms of production planning.     

Manufacturing environment-oriented robust tolerance optimization method

Tolerance design has a great impact on the cost and quality of a product. Previous research focused on process tolerances or robust tolerance design with little consideration on real manufacturing context. This paper presents a nonlinear method for robust tolerance design based on the real manufacturing context in three stages. The objective function to be minimized is the total manufacturing cost. The constraint equations for the optimization model are also deduced, which select suitable manufacturing processes based on the manufacturing environment. Simulation annealing (SA) is used for the nonlinear optimization. The approach is finally illustrated by a practical example. The results of the comparison with different models indicate that the proposed approach is more effective with the manufacturing resource. The robust and reliable tolerance can be obtained.     

Optimal target selection for unbalanced tolerance design

In many manufacturing processes, unbalanced tolerance design is a common occurrence. It occurs when the deviation of a quality characteristic in one direction is more harmful than in the opposite direction. The failure mode in these two directions is usually different. Furthermore, automatic inspection and measurement technology are widely used by the industries. The non-conforming part will be detected automatically. Thus, a truncated asymmetrical quadratic loss function is assumed for the unbalanced tolerance design. Traditionally, the manufacturer would either choose the smaller tolerance as the tolerance for both sides, or would set the process mean at the middle of the tolerances. Both methods fail to minimise the expected quality loss. The purpose of this paper is to find out the optimal manufacturing setting such that the expected quality loss is minimised. The results show that the process mean should be shifted a little from the target value.